Household wall receptacles (outlets) provide power (in the US, 120 VAC) from the power company "mains" to appliances plugged into the receptacles. Typically, new construction codes require certain receptacles, typically those which either are in a bathroom or on an exterior of a house, to be ground-fault protected. Generally, ground-fault protection involves opening a circuit when a threshold current imbalance has been detected between two legs of a circuit. The operation of ground-fault protectors is well known, and does not form a part of the present invention, per se.
Ground-fault protection can be implemented either at the circuit breaker box by providing a GFI breaker, or can be implemented at a wall receptacle location by using a GFI receptacle in lieu of a "standard" wall receptacle. For homes without ground-fault protection, or in instances where a homeowner desires to add ground-fault protection to one or more wall receptacles, either GFI breakers or GFI receptacles can be retrofitted. However, doing so requires "playing with electricity", an activity which is shunned by many homeowners.